Ice making machine and method

ABSTRACT

A method and apparatus for congealing liquids wherein a refrigerating fluid carries heat away from one side of a heatconducting wall and a congealed layer is formed on the other side of the wall. The amount of refrigerating liquid supplied to the wall surface is reduced when the congealed layer builds up sufficiently to produce a major heat transfer bottleneck. The apparatus has a freezing cylinder drum which rotates in a body of water with its top portion above the water surface where an internal roller deflects the cylindrical drum and peels the ice free. The ice contains a low concentration of boron which is substantially identical with the concentration of boron in the water.

United States Patent 191 Field [451" Dec. 4, 1973 ICE MAKING MACHINE ANDMETHOD Primary Examiner-William E. Wayner [76] 'Inventor: Crosby Field,8029 Harbor View Stuns et Ter., Brooklyn, N.Y. 11209 ST [57] AB RACT 22F'] d: F b. 23 1972 y 1 e A method and apparatus for congealing liquids[21] App 228,554 wherein a refrigerating fluid carries heat away fromone side of a heat-conducting wall and a congealed [52] US Cl 62/7262/346 165/91 layer is formed on the other side of the wall. The [51]nit.ct"IIIIIIIIIIIIIIIIIIIII .7. as, W ofreffigemfing a supplied to thewall 58 Field of S earch 62/345 354, 346 face is reduced when thengea1ed layer builds up 62/66 165/90 sufficiently to produceamajor heattransfer bottleneck. The apparatus has a freezing cylinder drum [56]References Cited which rotates in a body of water with its top portionabove the water surface where an internal roller de- UNITED STATESPATENTS fleets the cylindrical drum and peels the ice free. The2,054,101 9/1936 Short ..'62/345 X i contains a low concentration ofboron which is 3,403,532 10/1968 Knowles 62/354 X Substantiallyidentical with the concentration of boron in the water.

10 Claims, 3 Drawing Figures in particular to freezing water solutionsin an improved and dependable manner.

An object of this invention isto provide machines and methods forcongealing liquids which are more efficient and economical than thosepreviously available. A further object is to provide for congealingliquids in a manner which is not handicapped from the standpoint ofeconomy and performance because of high heat barrier characteristics ofthe congealed product. In the past, ice and other congealed productshave been produced by utilizing secondary refrigerant liquids such asbrine and glycol-water solutions. The refrigerant liquid is cooled in anevaporator-chiller of a refrigeration system and is then pumped througha congealing machine or unit having a flexible wall of highheatconductivity with a freezing surface on one side upon which a layerof the congealed product is formed, and the refrigerant liquid flowsalong the other side of the wall and carries away the heat extractedfrom the liquid being congealed. The present invention constitutes animportant improvement in such congealing methods and apparatus.

In the illustrative embodiment of the present invention, an ice makingor congealing machine is used which is of the type disclosed in my priorU.S. Pat. No. 2,257,904. The liquid to be congealed is a water solutioncontaining a predetermined concentration of boron, and the ice which isformed contains boron in the same or an insignificantly differentconcentration. In the illustrative embodiment, the congealed product isutilized as a safety mechanism in the event of an explosion of a nuclearreactor in a power plant, the ice being available to act as a radiationand heat sink" to absorb instantaneously large quantities of radiationand heat 'with a minimum rise in temperature and pressure. However, itis understood that the invention machine 2 is of the general type shownin my U.S. Pat.

No. 2,257,904. Machine 2 has a flexible cylinder 4. immersed other thanat its top in a body 6 of a water solution in a tank 8. Cylinder 4 hasan exterior freezing surface 52, and is mounted at its ends by astructure (not shown) including end plates and stub shafts upon which itrotates about its axis 10. Within the cylinder there is a stationarystructure 14 which includes a deflecting roller 12 at the top and acylindrical drum sheet 16 which is substantially coaxial with thecylinder. The drum sheet is of slightly less radius than the cylinder sothat (see also FIG. 3) it is parallel to and spaced from the innersurface 50 of the cylinder. The drum sheet is perforated in accordancewith a pattern to be discussed below so as to provide holes in each ofwhich there is mounted a nozzle 18 from which a jet of cold brine isimpinged against the inner surface of cylinder 4. The cold brine isrecirculated to and from the cylinder in the manner disclosed in theabove-identified patent, first it is pumped under pressure axially intothe central space 17 surrounded by the drum sheet and it then flows withthe jet action through the nozzles into the toroidal space 19 (FIG. 3)between the drum sheet and the cylinder. The brine thenflows upwardlybetween the rows of jets to a top horizontal discharge passageway 21from which it is withdrawn through an axial discharge conduit (notshown). The pressure difference between space .17 and I9 insures astrong jet action projecting the brine jets through the body of brineagainst the internal surface 50 of the cylinder wall. As will beexplained below, the jets of brine circulate the surrounding body ofbrine and also brake up the liquid film on surface 50 so as to provide ahigh coefficient of heat transfer from the cylinder wall to the brine.

As shown schematically, the brine is cooled by passing it to and from anevaporator-chiller 20 which is part of a refrigeration system, whichalso includes a compressor 22, a condenser 24, a receiver 26, anexpansion valve 28 and other standard components not shown.

As an area of cylinder 4 rotates clockwise from the two oclock position30, its freezing surface 52 moves downwardly into the water solution anda layer of ice starts to form on the freezing surface. The thicknessincreases to approximately the It) oclock position 32 where the freezingsurface emerges from the water solution, and the ice is then sub-cooledas it moves on to the zone of deflecting roller 12. When passing overthe deflecting roller, the cylinder is deflected sufficiently to causetheice to peel away from the freezing surfaces in the form of a freeribbon of ice 34. Illustratively, the ice passes to a bin 36.

FIG. 2 shows the positioning of nozzles 18 on the drum sheet. Extendinglongitudinally of the drum sheet between the edges 40 and 42 are nineparallel active perimeter areas 43, each of which is separated from thenext by an inactive perimeter area 40'. In slightly more than one-halfof each active perimeter area adjacent the top edge 40, there is onenozzle per square inch of the active perimeter area, whereas. in thebottom portion which extends toward edge 42 there is one nozzle for eachtwo square inches of the active perimeter area. When the drum sheet 16is installed (FIG. 1) in cylinder 4, edge 40 is at the one o'clockposition 30, and edge 42 is at the 1 1:30 o'clock position. Hence, thejets of cold brine from each of the active. perimeter areas 42 forms aperimeter freezing zone on the freezing surface 52 of the cylinder. Eachof the freezing zones has an area extending approximately clockwise fromposition 30 which is subjected to thecooling effect of the cold brinefrom the larger number of the jets which are positioned one per squareinch, whereas the remainder of the freezing zone is subjected to thecooling effect of brine from the smaller number of jets which are spacedone per two square inches.

Referring now to FIG. 3, there is represented somewhat schematically, asection of cylinder 4 along a radial plane at position 32, where a layerof ice 34 is adhered to the freezing surface 52. In the initial stage ofthe formation of layer 34 a portion of the cylinder moves downwardlybelow the surface of the water solution and a small film of iceimmediately forms on surface 52. In this embodiment, the body 6 of thewater solution is at a temperature which may be substantially above itsfreezing temperature of 31.5F, and the cold brine at I0F is projectedthrough nozzles 18 in the form of the jets represented by arrows 54. Thespacing of the jets and the rate of delivery of brine is such thatsurface 50 is maintained at substantially the temperature of the brine.Hence, at position 30 there is a temperature gradient of more than 41.5Fbetween the water solution at surface 52 and the brine at surface 50.However, the film of ice which forms immediately on surface 52 is a veryexcellent heat insulator, whereas cylinder 42 is a very excellent heatconductor. Therefore, the layer of ice soon becomes a much greaterheat-transfer barrier than the cylinder wall.

The jets of brine have sufiicient force to break up the liquid film onsurface 50 and the quantity of brine is sufficient to carry away theheat which passes to the cylinder wall through the layer of ice. Hence,the layer of ice builds up and the cylinder wall approaches thetemperature of the brine. Therefore, the present invention takes intoaccount, when the layer of ice reaches its maximum thickness,substantially the entire temperature gradient is between surface 56 and52, and the temperature gradient between the surfaces of the cylinderwall is negligible. The present invention takes into account the factthat the layer of ice is then the heattransfer bottleneck. That is, therate of heat transfer from surface 56 to the brine is limited by therate at which the heat will pass through the layer of ice at theexisting temperature gradient. However, the amount of brine circulatedis always sufficient to maintain a substantially OF temperature gradientacross the cylinder wall and substantially the entire temperaturegradient between the brine and the ice surface 56 is maintained acrossthe layer of the ice. That produces the maximum heat transfer to thebrine and therefore the maximum congealing rate for the brine and watertemperatures.

In accordance with the present invention, no more brine is circulatedthan is necessary to carry away the maximum amount of heat which willpass through the layer of ice as its thickness increases. Thecirculation of brine at a rate in excess of that amount would notincrease the rate of heat transfer from the ice surface and thereforewould not increase the congealing rate. The reduction in the amount ofbrine projected against the cylinder wall surface 50 when the ice layerbuilds up to a pre-determined value, does notreduce the temperaturegradient across the surfaces of the layer of ice, and the rate of heattransfer therethrough is maintained at the maximum value. As indicatedabove, the reduction in the rate of circulation of brine is effected byreducing the number of nozzles from one per square inch to one per twosquare inches of the active perimeter areas. However, the layer pf iceis still the heat-transfer bottleneck and there is still sufficientbrine circulation to maintain the entire cylinder wall in the freezingzones at substantially the temperature of the brine.

The reduction in the rate of circulation in the brine materiallyimproves the overall efficiency of the system and makes it possible tomaintain satisfactory operating conditions. The circulation ofunnecessary brine would produce an objectionable heat load, and anyreduction in such circulation is benficial to the system. For theparticular ice-making installation herein disclosed, only one-half theamount of brine is circulated for approximately one-half of each offreezing zones. That permits a reduction of the order of 25 percent inthe sizes of the brine handling and chilling components, i.e., pumps,lines and chiller. Also, as indicated, it reduces the overall size ofthe refrigeration system. Hence, there is a substantial reduction in theinitial cost of the installation as well as in the cost of theoperation.

An important aspect of the present invention is that nozzles 18 directdiscrete jets of brine against surface 50 so as to break down the filmson the surface and increase the rate of heat transfer between thecylinder wall and the brine. lllustratively, nozzles 18 have orifices of0.087 inch diameter, and the spacing between the nozzles and surface 50is of the order of 0.5 l inch. Each of the active perimeter areas 43 issubjected to intensive jet action, whereas the inactive areas 44 provideperipheral paths for the brine to flow upwardly beyond the edges 40 and42 of the drum sheet and thence axially to the discharge port (notshown). Hence, an efficient flow path is provided with the drum sheetforming an inlet chamber in which the brine is confined under pressureand from which it is discharged as jets impacting against surface, andthe brine from each jet then passes to the next adjacent inactive areaand along it upwardly to the axial discharge passageway.

The first film of ice is in the form of thin ribbons one directly overeach of the jets and having a cross-section in the form of a single baseellipticordial segment with its center directly over the center of itsjet. The layer then builds up by the merging of the separate ribbons asthe thickness increases. The increase in thickness of the ice beingfrozen follows the well known exponential law of growth, which may beplotted upon semilogatithmetic paper. The curve is a straight line whenshown in a coordinate graph the abscissae of which are time in equalincrements and the ordinates are the corresponding logarithms of thethicnkess of the ice. Tests show that the slope of the line changesabruptly at the ice thickness where the ice becomes the dominanttransfer barrier. Hence, those tests indicate one rate of ice growthuntil the ice becomes the dominant heattransfer bottleneck and anotherrate of ice build up thereafter.

In the illustrative embodiment, the refrigerating liquid is 28 percentcalcium cloride brine which has relatively low viscosity. Tests havealso been conducted with the refrigerant liquid formed by equal parts ofwater and ethylene glycol, which has relatively high viscosity. However,the jet action effectively breaks up the surface film even with the highviscosity solution.

I claim:

1. In the art of freezing thin layers of ice from a water solutioncontaining dissolved or dispersed other materials, the steps of,covering a freezing surface with the solution throughout a freezingzone, refrigerating said freezing surface through a conducting wall byprojecting a chilled liquid at a controlled temperature and at acontrolled quantity rate against the opposite surface of said wall toform an initial layer of ice on said freezing surface until the layer ofice is of a sufficient thickness to constitute a substantial heattransfer bottleneck between the solution and the chilled liquid andthereby reduce the heat transfer rate at which heat passes from thesolution to the chilled liquid at the temperature gradient between thechilled liquid and the freezing temperature of the solution, and thenreducing the quantity rate at which the chilled liquid is projectedagainst said surface to thereby reduce the quantity of chilled liquidprojected against a given area of said opposite surface to take intoaccount said reduced rate of heat transfer from the solution.

2. The method as described in claim 1 wherein said water solution isborated water and wherein said ice is borated ice of a thickness of 0.1inch and contains substantially the same concentration of boron as theborated water.

3. The method as described in claim 1 wherein the initial layer of icehas a thickness of 0.06 inch and the final thickness of the ice is ofthe order of 0.1 inch.

4. In the art of congealing liquids, the steps of, mov ing a wall havinga congealing surface thereon through a congealing zone within a body ofliquid to be congealed to said congealing surface, supplying refrigerantfluid at a determined effective temperature to the side of said wallopposite said congealing surface at a controlled rate throughout aninitial portion of said freezing zone to thereby form an. initial layerof congealed liquid which produces a decrease in the heat transfer rateat which heat is transferred from the liquid solution to the refrigerantfluid at the temperature gradient between the refrigerant fluid and thecongealing temperature of the liquid, and supplying said refrigerantfluid at a reduced rate to said opposite surface throughout thesubsequent portion of said freezing zone to thereby reduce the quantityof said refrigerant fluid delivered to a specific area of said oppositesurface to correspond to said reduced rate of heat transfer of heat fromsaid liquid. 1

5. In the art of congealing liquids as describedlin claim 4 wherein theliquid being congealed is water and the refrigerant fluid is brine, andwherein jets of brine are projected through a body of brine against saidwall with sufficient force to displace the liquid film on the wallsurface. 3

6. In the art of congealing liquids as described in claim 5 wherein saidwall is substantially cylindrical and flexible, the step of, rotatingsaid wall substantially about its axis. v t

7. In apparatus for congealing liquid, a substantially cylindrical metalwall having an exterior freezing surface and an internal refrigeratedsurface, means immersing said cylindrical metal wall in'a body of liquidexcept at its top portion, means for rotating said wall, nozzle meanspositioned along the part of and directed toward said refrigeratedsurface, supply means to project jets of refrigerated liquid from saidnozzle means against said refrigerated surface substantially throughoutthe path of its movement while being immersed, said nozzle means andsaid supply-means being constructed to deliver a predetermined quantityof said refrigerated liquid at a predetermined effective temperatureagainst a specific area of said refrigerated surface throughout itsmovement along the initial portion of its path immediately after beingimmersed to thereby form an initial layer of congealed liquid on saidfreezing sur face which reduces the heat transfer rate at which heatpasses fromsaid body of liquid to said refrigerated liquid at thetemperature gradient therebetween and supplying said refrigerated liquidat a reduced rate in a subsequent portion to thereby reduce the quantityof refrigerated liquid delivered to said specific area of therefrigerated surface in accordance with said reduction in the heattransfer rate of heat from the body of liquid.

8. An apparatus as described in claim 7 wherein said nozzle meanscomprises a nozzle plate and a plurality of nozzles mounted thereon inspaced relationship, said nozzles being spaced further from each otherin said subsequent portion than in said initial portion to provide saidreduced rate of liquid delivery.

9. Apparatus as described in claim 8 wherein the space between saidnozzle plate and said cylindrical wall is occupied by a body of liquidand said nozzle plate provides an inlet chamber for said refrigeratedliquid, and means to chill said refrigerated liquid and said nozzlemeans.

1. In the art of freezing thin layers of ice from a water solutioncontaining dissolved or dispersed other materials, the steps of,covering a freezing surface with the solution throughout a freezingzone, refrigerating said freezing surface through a conducting wall byprojecting a chilled liquid at a controlled temperature and at acontrolled quantity rate against the opposite surface of said wall toform an initial layer of ice on said freezing surface until the layer ofice is of a sufficient thickness to constitute a substantial heattransfer bottleneck between the solution and the chilled liquid andthereby reduce the heat transfer rate at which heat passes from thesolution to the chilled liquid at the temperature gradient between thechilled liquid and the freezing temperature of the solution, and thenreducing the quantity rate at which the chilled liquid is projectedagainst said surface to thereby reduce the quantity of chilled liquidprojected against a given area of said opposite surface to take intoaccount said reduced rate of heat transfer from the solution.
 2. Themethod as described in claim 1 wherein said water solution is boratedwater and wherein said ice is borated ice of a thickness of 0.1 inch andcontains substantially the same concentration of boron as the boratedwater.
 3. The method as described in claim 1 wherein the initial layerof ice has a thickness of 0.06 inch and the final thickness of the iceis of the order of 0.1 inch.
 4. In the art of congealing liquids, thesteps of, moving a wall having a congealing surface thereon through acongealing zone within a body of liquid to be congealed to saidcongealing surface, supplying refrigerant fluid at a determinedeffective temperature to the side of said wall opposite said congealingsurface at a controlled rate throughout an initial portion of saidfreezing zone to thereby form an initial layer of congealed liquid whichproduces a decrease in the heat transfer rate at which heat istransferred from the liquid solution to the refrigerant fluid at thetemperature gradient between the refrigerant fluid and the congealingtemperature of the liquid, and supplying said refrigerant fluid at areduced rate to said opposite surface throughout the subsequent portionof said freezing zone to thereby reduce the quantity of said refrigerantfluid delivered to a specific area of said opposite surface tocorrespond to said reduced rate of heat transfer of heat from saidliquid.
 5. In the art of congealing liquids as described in claim 4wherein the liquid being congealed is water and the refrigerant fluid isbrine, and wherein jets of brine are projected through a body of brineagainst said wall with sufficient force to displace the liquid film onthe wall surface.
 6. In the art of congealing liquids as described inclaim 5 wherein said wall is substantially cylindrical and flexible, thestep of, rotating said wall substantially about its axis.
 7. Inapparatus for congealing liquid, a substantially cylindrical metal wallhaving an exterior freezing surface and an internal refrigeratedsurface, means immersing said cylindrical metal wall in a body of liquidexcept at its top portion, means for rotating said wall, nozzle meanspositioned along the part of and directed toward said refrigeratedsurface, supply means to project jets of refrigerated liquid from saidnozzle means against said refrigerated surface substantially throughoutthe path of its movement while being immersed, said nozzle means andsaid supply means being constructed to deliver a predetermined quantityof said refrigerated liquid at a predetermined effective temperatureagainst a specific area of said refrigerated surface throughout itsmovement along the initial portion of its path immediately after beingimmersed to thereby form an initial layer of congealed liquid on saidfreezing surface which reduces the heat transfer rate at which heatpasses from said body of liquid to said refrigerated liquid at thetemperature gradient therebetween and supplying said refrigerated liquidat a reduced rate in a subsequent portion to thereby reduce the quantityof refrigerated liquid delivered to said specific area of therefrigerated surface in accordance with said reduction in the heattransfer rate of heat from the body of liquid.
 8. An apparatus asdescribed in claim 7 wherein said nozzle means comprises a nozzle plateand a plurality of nozzles mounted thereon in spaced relationship, saidnozzles being spaced further from each other in said subsequent portionthan in said initial portion to provide said reduced rate of liquiddelivery.
 9. Apparatus as described in claim 8 wherein the space betweensaid nozzle plate and said cylindrical wall is occupied by a body ofliquid and said nozzle plate provides an inlet chamber for saidrefrigerated liquid, and means to chill said refrigerated liquid anddeliver it to said inlet chamber at a pressure sufficient to cause it toflow through said nozzles and displace the liquid film on the adjacentwall surface.
 10. Apparatus as described in claim 7 which includes arefrigeration system with an evaporator-chiller through which saidrefrigerated liquid is circulated to said nozzle means.